# Piezoelectric Sensors Change with Frequency

Discussion in 'General Electronics Chat' started by rperea, Oct 16, 2009.

1. ### rperea Thread Starter Member

Apr 7, 2009
15
0
I am trying to explain why the voltage increases when the frequency increases. I am testing a piezoplate at 1Hz and 2Hz, 10 cycles and a force of 30N. I collect the voltage difference. The votlage increases with frequency.

The equations for piezoelectricity are:

ε = SE * σ  da 33* Efield
Electric Displacement = d33a * σ + (Permitivity) * Efield {Eq. 4}

So.....what parameter depends on frequency? Is it the permitivity?

2. ### beenthere Retired Moderator

Apr 20, 2004
15,815
283
Probably the piezo element is rate sensitive. Shake it faster and get a higher output for a given force applied.

There is probably some resonant point where the mechanical energy is coupled most efficiently - a simple experiment should should a peak output at that frequency.

Last edited: Oct 16, 2009
3. ### rperea Thread Starter Member

Apr 7, 2009
15
0
Thanks for the reply. What do you mean rate senstitive? I knoe the higher the frequency the higher the voltage I will get....now I am trying to understand this concept in the constitutive equations.....where thats the frequency play?

4. ### beenthere Retired Moderator

Apr 20, 2004
15,815
283
The higher the frequency, the higher the rate of change.

5. ### BillB3857 Senior Member

Feb 28, 2009
2,402
348
Assuming you are using a uniform level of mechanical excitation, and plot the distance of excursion vs time, you will see that the rate of change in position is faster at higher frequencies.

6. ### rperea Thread Starter Member

Apr 7, 2009
15
0
Again, is permitivity a function of frequency?
Where does the frequency rate play the role in the consitutive equations?

Sorry to be so confusing.

7. ### BillB3857 Senior Member

Feb 28, 2009
2,402
348
I found this equivalent circuit of a piezo transducer. The series capacitance will explain the increased output at increased frequency. Xc=1/2πfc.

File size:
6.8 KB
Views:
17